Homicide investigators have released security video of the attack they said happened when Tam refused to hand over his bag to the suspects. The pair chased him down and fled with Tam’s bag as he lay sprawled in the road between Franklin and Gough streets, police said.

San Francisco police said the stabber is a 5-foot-10 man seen in a hoodie in surveillance footage of the attack.

(San Francisco Police Department)

Police said his famale accomplice is 5-foot-4 and wears her hair in dreads or braids.

(San Francisco Police Department)

San Francisco police said the stabber is a 5-foot-10 man seen in a hoodie in surveillance footage of the attack. Police said his famale accomplice is 5-foot-4 and wears her hair in dreads or braids.

Investigators described the woman as a 5-foot-4 black or mixed-race adult with dreadlocks or braids and the man seen in the footage stabbing Tam in the head as a 5-foot-10 black adult of heavy build.

“He took only a bag of items and killed someone for it,” San Francisco police Officer Carlos Manfredi told KGO-TV. “If he could do it to this person, he could do it to someone else.”

Paul Tam, 48, a recent immigrant to the United State from Manchester, England, was visiting San Francisco with his neice the night of the attack. He died just over a month later.

(Facebook)

Police asked anyone who might know the suspects to contact the homicide detective team probing the case. The San Francisco Police Officer's Association has promised a $5,000 reward for information leading to their arrest.

Tam had been visiting San Francisco with his niece shortly after he moved to California from Manchester to work as a freelance IT specialist, The Telegraph reported. She witnessed the attack but escaped unharmed.